The present invention relates to a micro sample tube for holding a sample in an automated sampling system. More particularly, the present invention relates to a micro sample tube having a) a standard size exterior so as to allow for marking with, for example, bar codes, and so as to allow for use in an automated analyzer geared for holding and/or moving of sample tubes of a same standard size, b) a uniquely designed interior for minimizing internal dead volume, as well as for decreasing the incidence of detrimental impact of a sample probe against an interior wall of the micro sample tube, and c) an improved structure for increasing heating and/or cooling of the sample tube.
Automated sample handling systems are known which automatically dispense patient fluid samples, such as blood plasma, along with reagents and other additives, into the reaction well of a cuvette which is then automatically positioned for monitoring or performing tests on the fluid sample. For example, in U.S. application Ser. No. 07/833,950, now U.S. Pat. No. 5,236,666, to Hulette et al, entitled xe2x80x9cTemperature Regulation in a Sample Handling System for an Optical Monitoring Systemxe2x80x9d, there is disclosed an automated sample handling system for an optical evaluation instrument that can handle a high throughput of patient samples with a high degree of versatility, adaptability and reliability. The invention according to Hulette et al allows for walk-away automation for a sample handling system, once sample tubes containing patient samples are loaded into the system.
Accurate positioning and stabilizing of the sample tube within an automated system is essential. For example, in the aforementioned system disclosed by Hulette et al, a sample tube is advanced to a piercer where a piercing probe can be caused to pierce the septum of the sample tube. This step would be omitted, of course, should a sample tube without a cap be used. A sample probe is lowered a predetermined distance into the sample tube to aspirate a programmed amount of sample. The sample probe is then removed from the sample tube and the sample subsequently dispensed into a cuvette. Accurate positioning of the probe into the sample tube, without gouging or puncturing the internal side wall of the sample tube, is important.
Automated analyzers have been developed which can automatically perform analyses on multiple patient samples without operator intervention, where it is possible to track specific patient samples by means of bar code labels. Sample volume containers with bar code information on the side identifying the sample and the test to be performed by the analyzer are loaded into, for example, a temperature controlled compartment, which also stores reagents and other additives under temperature control. The samples are automatically dispensed into reaction wells of cuvettes, and reagents and possibly other additives are automatically combined with the test samples according to the programmed test read from the bar code on the sample container. The reaction wells containing a reaction volume composed of a test sample and additives are transported to an optical analyzer which monitors changes in optical characteristics of the reaction volume, which changes are processed and evaluated according to the particular test being performed. Such a machine is capable of reading the bar codes on hundreds of patient samples, keeping track of such patient samples, and performing tests on such samples without intervention of the operator once the sample containers are loaded into the temperature controlled compartment. As such, the ability to have a bar code on the exterior of a sample container, regardless of the sample size, is important for the automated analysis.
Regarding the temperature control of the samples, a temperature controlled housing can be provided for storing the fluid samples and reagents at a relatively cool temperature for preventing degradation of the samples and reagents at a temperature of, for example 4 degrees C. For this reason, a micro sample tube with improved heat transfer capabilities, would be desirable.
Sample tubes are manufactured in various brands and sizes. For example, sample tubes manufactured by Beckton Dickinson of Rutherford, N.J. and sold under the brand name Vacutainer with Hemogard Closure, typically have a length of 75 mm and a diameter of 13 mm. In contrast, sample tubes made by Sarstedt and sold under the brand name of Monovette Microtainer can have a length of 65 mm and a diameter of 12 mm. Consequently, the aforementioned automated systems typically are limited to using one standard size of sample tube for all tests and procedures to be run, or by requiring that all of the sample tubes of a particular transport rack be of the same size. However, at times when very small quantities of a sample are analyzed, an undesirably large amount of sample fluid remains in a standard size sample tube and cannot be removed by the sample probe. This remaining fluid (dead volume) is therefore wasted and tests that otherwise might have been performed, are foregone.
It is therefore an object of the invention to provide a sample tube for an automated analyzer that, on the exterior, is of a standard size so as to be easily handled by the analyzer, and so as to allow for the placement of a bar code label on an exterior surface of the sample tube.
It is another object of the invention to provide a sample tube with a standard size on the exterior, but with a restricted internal volume so as to allow handling of small volume samples, but with a minimum of dead space within the sample tube.
It is a further object of the present invention to provide a sample tube of standard size exterior, and restricted size on the interior, with interior walls having a unique structure that helps avoid gouging of the walls of the restricted interior by an automated fluid sampling probe.
It is yet another object of the present invention to provide a sample tube having an exterior structure which aids in heating and/or cooling of the sample tube.
The above and other objects are accomplished according to the invention by the provision of a sample tube having an outer wall defining an exterior of the sample tube, the cross section of which is substantially circular with substantially constant cross sectional area along the length of the tube, the outer wall defining a central axis of the sample tube, an open end at one axial end of the sample tube, and a closed end at the other axial end of the sample tube, and an inner wall defining an interior of the sample tube, the inner wall having in at least a portion thereof, a slope towards the central axis of the sample tube in the direction of the closed end, the slope of the inner wall in cross section, defining a portion of a circumference of a circle. Fins may be provided extending from the inner wall and defining in part the outer wall.
The invention will be described below in greater detail in connection with an embodiment thereof that is illustrated in the drawing figures.